1. Field of the Invention
The present invention relates to a semiconductor device which transmits and receives data and detects a distance by wireless signals.
2. Description of the Related Art
In recent years, small semiconductor devices in each of which an ultrasmall IC chip and an antenna for wireless communication are combined (hereinafter also referred to as a semiconductor device or an RF chip and also called an RFID tag, a wireless tag, an ID tag, or an RF tag) have attracted attention. This semiconductor device can perform data transmission and reception, such as data writing or data reading, without contact by transmission and reception of communication signals using a wireless communication device (hereinafter also referred to as a reader/writer).
An example of fields of application of a semiconductor device which performs data transmission and reception by wireless signals is product management for the distribution industry. Product management using barcodes and the like is the mainstream at present; however, since barcodes are read optically, data cannot be read in some cases where there is an interrupting object. On the other hand, when data are transmitted and received with the use of a wireless communication device without contact, data of the semiconductor device are read wirelessly; thus, data can be read even when there is an interrupting object. Therefore, an improvement in efficiency, a reduction in cost, and the like of product management are expected. In addition, a broad range of applications such as for tickets, airline tickets, or automatic fare payment has been expected (see Japanese Published Patent Application No. 2000-149194). A system such that people and objects are identified and managed by a small semiconductor device which transmits and receives data by wireless communication is called RFID (Radio Frequency Identification) and has attracted attention as fundamental technology of the IT society.